Method for operating an oxygen blowing lance in a metallurgical vessel and a measurement system for determining a measurement signal used in the method

ABSTRACT

A method for operating a blowing lance for blowing a gas in a metallurgical vessel, wherein the head of the blowing lance includes at least one supersonic nozzle, operating parameter measurement signals used for the purpose of process control are continuously acquired. The inlet pressure and/or the inlet temperature of the gas at the supersonic nozzle and/or the vibration amplitude and/or the vibration frequency of the blowing lance and/or the time at which ignition occurs during the oxygen blowing process and/or the location at which ignition occurs during the oxygen blowing process is detected and/or measured in the head of the lance by a detector or sensor arranged in the head of the lance near the supersonic nozzle during operation of the blowing lance. The measurement signal(s) are transmitted to a control unit connected to the detector or sensor and made available for controlling the operation of the blowing lance.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority of DE 10 2013 208 079.4, filedMay 2, 2013, the priority of this application is hereby claimed and thisapplication is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention pertains to a method for operating a gas-blowing lance,especially an oxygen blowing lance, in a metallurgical vessel, whereinthe preferably replaceable head of the blowing lance comprises at leastone supersonic nozzle. The invention is also directed at a measurementsystem for determining measurement signals used during the operation ofa gas-blowing lance, especially an oxygen blowing lance, in ametallurgical vessel for the purpose of process control, wherein themeasurement system includes a blowing lance, preferably an oxygenblowing lance, with a preferably replaceable head comprising at leastone supersonic nozzle, and an evaluation and/or process control unit toreceive and process the measurement signals.

In certain methods of steel production such as the basic oxygen furnace(BOF) method or the argon-oxygen decarburization (AOD) method, it isconventional practice to subject the molten metal in the metallurgicalvessel to a flow of a gas, especially a flow of oxygen (O₂) or nitrogen(N₂). For this purpose, a blowing lance is typically lowered into themetallurgical vessel from above, and the gas is blown from it onto themolten metal.

Gas can also be blown onto the melt in processes involving the meltingof scrap in an electric-arc furnace (EAF). Gas is usually blown onto themelt at least in the following metallurgical units: BOF converters, AODconverters, the burner and injector nozzles for an electric-arc furnace(EAF) or a CONCARC furnace (CON=converter, ARC=arcing), the burner andinjector nozzles for a reducing furnace (SAF=submerged arc furnace), andthe nozzles for vacuum treatment systems such as VOD (Vacuum OxygenDecarburization) or RH (Ruhrstahl-Heraeus) units. During the productionof steel in a BOF converter, the oxygen is blown onto the metal bath bymeans of the blowing lance. The head of the lance is typically 1.4-3 maway from the surface of the bath. In the head of a blowing lance ofthis type there are usually several convergent-divergent nozzlesarranged at previously determined angles, which accelerate the gas tosupersonic speed. The convergent-divergent nozzles are called“supersonic” or “Laval” nozzles. The gas typically leaves thesesupersonic nozzles at approximately twice the speed of sound and with agreat deal of momentum, whereupon it strikes the metal bath. In themolten metal bath, an oscillating blowing trough is formed, and theblown-on gas ensures an intensive decarburization reaction. A foamy slagforms on the molten metal bath as a result of the gaseous reactionproducts which rise up.

According to isentropic stream filament theory, the geometry of a Lavalor supersonic nozzle can be designed for only a single value—namely itsideal operating point or “design point”—with respect to any one case ofthe inlet pressure p₀ of the supersonic nozzle, the inlet temperature T₀of the nozzle, and the static backpressure p_(A) in the metallurgicalvessel. The inlet pressure p₀ at this ideal operating point is thereforealso called the design pressure, and the inlet temperature T₀ at thisideal operating point is also called the design temperature. Only whenthe supersonic nozzle is operated at its ideal operating point does theexpanded stream of gas lie solidly against the nozzle wall until leavingthe nozzle and is the gas accelerated to supersonic speed. As soon asthe real flow through the nozzle deviates from the ideal design state orideal operating point, however, complex flow patterns (diamond wavepatterns) in the form of expansion waves or density surges develop bothinside and outside the nozzle, which can cause wear of the nozzle edgeand lead to premature separation of the jet from the nozzle wall. Whenthe cold gas jet separates from the nozzle wall, a recirculation regiondevelops, which allows hot converter gas to reach the nozzle wall, as aresult of which the nozzle suffers wear. To reduce or prevent such wearof the nozzle, the supersonic nozzle must therefore be operated at itsoperating point as consistently as possible.

At the tip of a blowing lance there is a replaceable head, which,depending on the application, includes several convergent-divergentsupersonic or Laval nozzles to accelerate the gas to supersonic speed. Alance head of this type can be used in the following types ofmetallurgical vessels or units, among others: in BOF and AOD converters,in SIS (Siemag Injection System) injectors for electric-arc furnaces(EAF), in reducing furnaces (SAF), and in vacuum systems (RH, VOD).

With respect to both the immediate inlet pressure p₀, i.e., the designpressure of the supersonic nozzle in question, and the inlet temperatureT₀, i.e., the associated design temperature of the supersonic nozzle,the geometry of a supersonic or Laval nozzle can be designed for onlyone optimal operating point of the associated supersonic nozzle at astatic backpressure p_(A) in the associated metallurgical vessel orunit. Only when both of the process variables, i.e., the designpressure/inlet pressure and the inlet temperature/design temperature,are maintained during converter operation will the supersonic or Lavalnozzle work at its optimal operating point and will the nozzle sufferonly minimal wear. Normally, during operation in practice, the upstreampressure p_(vs) and the volume flow rate of the gas are measured at avalve station where the gas is made available to the blowing lance.These are variables which are usually used in the design of theultrasonic nozzle. Thus the pressure loss Δp_(verl) occurring downstreamfrom the valve station, i.e., in the pipelines and pressure hoses,including the entire blowing lance, is estimated in order to determinethe inlet pressure p₀ on the basis of the equation p₀=p_(vs)−Δp_(verl).The exact pressure loss Δp_(verl) is difficult to determinetheoretically, because to do this it is necessary to perform acompressible pressure loss calculation for all the components, for whichpurpose the exact layout of the gas lines must be known. For thisreason, the process variables p₀, T₀, and p_(A) required for nozzledesign are always known in the form of approximations. Whether thesupersonic or Laval nozzle in question will then in fact work at itsdesign point or ideal operating point during practical use in the steelmill is uncertain. If it does not, the service life of the lance and thestability of the process will become worse.

During the blowing process, furthermore, the oxygen jet emerging fromthe blowing lance ignites when it makes contact with the liquid pigiron. Because the converter or the metallurgical vessel in question isoften filled not only with pig iron but also with coolants such as steelscrap, the oxygen jet emerging from the blowing lance can also be thrownback by the scrap, if its temperature is not high enough for ignition.Thus very often the combustion of the oxygen does not start immediately,i.e., as soon as the blowing process begins. It is extremely important,however, to know the exact time at which ignition occurs, becauseknowing when the associated decarburization reaction of the molten metalbath begins is vital to the management of the process. Depending on theposition of the scrap and the position of the liquid pig iron in thevessel, furthermore, the ignition time can also be different for eachnozzle of a multi-hole blowing lance. Differentiated knowledge of thetime and place of ignition would make it possible to achieve acorrespondingly exact differentiation according to the oxygen that isused and that which is not.

Finally, a melt-slag emulsion forms in the converter or metallurgicalvessel during conventional blowing processes. As a result of thedecarburization reaction, the volume of slag increases enormously, sothat slag can actually be ejected, which results in an increase inproduction costs and the risk of a shutdown. During the blowing process,furthermore, slag and molten metal, especially liquid steel, adhere tothe blowing lance, which is usually water-cooled. This skull which formson a blowing lance is undesirable and must be removed, because theoverall mass of the blowing lance increases undesirably and the orificesof the supersonic nozzles can become partially clogged.

A method for operating an oxygen blowing lance in a metallurgical vesselis known from WO 2012/136698 A1, in which the pressure and thetemperature are measured at the entrance to a supersonic nozzle of ablowing lance by means of an independent measurement device, which,without external supply lines or feed lines, performs time-resolvedpressure and/or temperature measurements and stores the correspondingmeasurement values. An independent measuring device of this type, alsocalled a “data logger”, is installed in the head of the blowing lanceand then measures the pressure and/or the temperature over the course ofits (battery-operated) service life and stores these data. Theindependent measurement device is then removed from the head of thelance and, after the measurement data have been read out, a calibrationcurve is set up. The operation of the oxygen blowing lance, which nolonger carries the independent measuring device, is then controlled onthe basis of this calibration curve. The disadvantage of using dataloggers is that the pressure loss Δp_(verl), the inlet pressure p_(0t)present during the course of operation, and the inlet temperature T_(0t)present during the course of operation can be determined only after thefact, i.e., after the lance has been taken out. The inlet pressurep_(0t) and the inlet temperature T_(0t) are not recorded continuously inreal time during the blowing process, which means that it is notguaranteed that the supersonic nozzle of the blowing lance will operateat its ideal operating point during the course of operation.

It is known from practical experience, furthermore, that conventionalvibration sensors mounted on the carriage of the lance can be used todetect vibrations of the blowing lance during operation in ametallurgical vessel. The measurement signals thus acquired can be usedto draw conclusions concerning the extent to which slag has formed inthe metallurgical vessel and the tendency to eject slag. The vibrationmeasurements are made on the carriage, because the vibration sensors areprotected from heat there and because the lance can be replaced withouthaving to worry about the sensors. The disadvantage of this solution isthat the vibrations measured on the carriage are much weaker than thosewhich occur at the tip of the lance, which is the area most affected byslag formation, and they can also be influenced by variables which areindependent of the process. Thus the acquired measurement signalsprovide only an imprecise picture of the conditions in the area of thetip of the lance. In addition, in the case of measurements which areconducted above the lance dome, the deflections of the blowing lance arenot detected in optimal fashion. Finally, in the case of measurementsensors mounted near the blowing lance dome, there is the danger thatthey can suffer wear and be damaged as a result of the heat to whichthey are subjected and the effect of the dust acting on them.

It is known from WO 2011/151143 A2 that a camera comprising CCD sensorsor photodiodes placed in the gap between the converter mouth and theexhaust hood can be used to measure the course of the radiationintensity over time and to determine the time at which a previouslydetermined radiation intensity is reached or at which a previouslydetermined increase in radiation intensity occurs, which is the point intime at which the oxygen jet emerging from the blowing lance ignites.This method for determining the time of ignition during the blowingprocess on the basis of observation, from the outside, of the lightemissions from the arcing zone which forms at the time of ignitionsuffers from the disadvantage that, as a result of the large amount ofsmoke generated after ignition, information on the ignition process canbe obtained only indirectly via the radiation of this smoke. As aresult, the reliability of the measurement result is limited. Inaddition, it is impossible to determine in a differentiated manner theignition of the individual oxygen jets, usually five to six, emergingfrom a multi-hole nozzle.

SUMMARY OF THE INVENTION

The invention is based on the goal of creating a solution which makespossible the continuous detection of operating parameter measurementsignals for the purpose of process control during the operation of agas-blowing lance, especially an oxygen blowing lance, in ametallurgical vessel.

In a method of the type described in detail above, this goal is achievedaccording to the invention in that the inlet pressure p_(0t) and/or theinlet temperature T_(0t) of the gas at the at least one supersonicnozzle and/or the vibration amplitude A and/or the vibration frequency ωof the blowing lance and/or the time at which ignition occurs during theoxygen blowing process and/or the location at which ignition occursduring the oxygen blowing process is/are detected and/or measured,preferably continuously, during the operation of the blowing lance,especially during a blowing process, preferably an oxygen blowingprocess, by means of at least one detector or sensor mounted in the headof the lance in the area of the supersonic nozzle, and in that themeasurement signal(s) thus obtained during operation of the blowinglance is/are transmitted, preferably on-line, to an evaluation and/orprocess control unit connected to the at least one detector or sensorand made available for the purpose of controlling the operation of theblowing lance.

In the case of a measurement system of the type described in detailabove, the previously mentioned goal is again achieved in that adetector or sensor is mounted in the head of the lance in the area ofthe at least one supersonic nozzle, which detector or sensor, isconnected by appropriate transmission means to the evaluation and/orprocess control unit; detects and/or measures, preferably continuously,in the head of the lance, during the operation of the blowing lance,especially during a blowing process, preferably an oxygen blowingprocess: the inlet pressure p_(0t) and/or the inlet temperature T_(0t)of the gas at the at least one supersonic nozzle and/or the vibrationamplitude A and/or the vibration frequency ω of the blowing lance and/orthe time at which ignition occurs during the oxygen blowing processand/or the location at which ignition occurs during the oxygen blowingprocess; and transmits, preferably on-line, the measurement signal(s)thus acquired during the operation of the blowing lance are transmittedto the evaluation and/or process control unit connected to the at leastone detector or sensor and makes them available for the purpose ofcontrolling the operation of the blowing lance.

The invention thus proceeds from the central idea of mounting, in thehead of the blowing lance, one or more detectors and/or sensors, whichdetect operating parameters by suitable measurement technology duringoperation, that is especially during the time that the blowing lance isin its working or operating position in the metallurgical vessel and isdelivering the gas, and transmit the acquired measurement signalscontinuously and on-line during operation to an evaluation and/orprocess control unit and thus make them available for the purpose ofcontrolling the operation of the blowing lance. The measurement signalsobtained in this way, which represent the current operating state inrelation to the operating parameters in question, can then be useddirectly for the purpose of process control during ongoing operation ofthe blowing lance.

According to one aspect of the invention, the current inlet pressurep_(0t) of the gas at the entrance to the at least one supersonic nozzleof the blowing lance is detected and/or measured by means of at leastone detector and/or sensor. According to a second aspect of theinvention, the inlet temperature T_(0t) of the gas at the entrance tothe at least one supersonic nozzle of the blowing lance is detectedand/or measured during the blowing process in the head of the lance,especially continuously, by means of at least one detector or sensor.

The operating parameter measurement signals acquired in the first aspectand/or in the second aspect of the invention are then transmitted to anevaluation and/or process control unit directly, preferably on-line, andmade available for the purpose of controlling the operation of theblowing lance. Thus it is possible, for example, to adjust the valvepressure p_(vs) and thus regulate the inlet pressure p_(0t) currentlybeing reached at the entrance to the supersonic nozzle in the head ofthe lance, this inlet pressure being set to a value which corresponds atleast essentially and/or approximately, i.e., with perhaps only a smalldeviation, to the design pressure p₀. It is therefore possible in thisway, by means of the invention, to operate a supersonic nozzle—and inthe case that a detector or sensor is provided at the entrance to eachsupersonic nozzle or Laval nozzle of a blowing lance—to operate all ofthe supersonic nozzles at all times at a point which is at least closeto their design point, that is, in or at their ideal operating point. Asa result, stable process conditions for the gas-blowing process areobtained, especially for oxygen blowing, which leads to a significantincrease in durability and to a longer service life of the preferablyreplaceable head of the lance. Continuous detection of the inletpressure p_(0t) and of the inlet temperature T_(0t) during a blowingprocess therefore makes it possible to adjust the pressure p_(vs)dynamically at the valve station during the blowing process, so that thehead of the lance can be operated at its design point and nozzle wearcan be minimized.

According to the invention, therefore, the current inlet pressure p_(0t)and the current inlet temperature T_(0t) present at the moment inquestion in the interior of the blowing lance, that is, in the head ofthe lance, are measured during the blowing process. This time-dependentpressure and temperature measurements are carried out by means ofdetectors and/or sensors. The measurement data are transmitted over acable or possibly wirelessly to a connected evaluation and/or processcontrol unit such as a PC. The power required to operate the detectorsand/or sensors can be supplied over the cable or by a battery or bymeans of an energy-harvesting module.

According to these first two aspects of the invention, therefore,pressure and possibly temperature sensors for determining the currentinlet pressure p_(0t) and the current inlet temperature T_(0t) of theoxygen or of the blowing gas in the blowing lance are installed in theblowing lance or directly in the head of the lance. At the same timethat the pressure measurement(s) is/are being carried out in the blowinglance or in the head of the lance, the pressure or upstream pressurep_(vs) at the valve station supplying the blowing gas or the oxygenshould also be measured. This makes it possible to perform an on-linecalculation of the pressure loss Δp_(verl)=p_(vs)−p_(0t) and to monitorthe deviation of the current inlet pressure p_(0t) and the current inlettemperature T_(0t) of the blowing gas or of the oxygen from thecorresponding design variables of the supersonic nozzle in question,namely, from the design pressure p₀ and the design temperature T₀,during the blowing process. The upstream pressure p_(vs) at the valvestation can thus be adjusted in such a way that an inlet pressure p_(0t)which corresponds to the design pressure p₀ is present at the entranceto one or all of the supersonic or Laval nozzles of the blowing lance.This has the effect of minimizing the wear of the head of the lance. Thevariable T_(0t) is not necessary for actual operation, but the designtemperature T₀ is required as a theoretical design variable for thenozzle design. It is not possible to determine the static pressure p_(A)in the metallurgical vessel in this way. For the design of the nozzle,however, this parameter plays only a subordinate role, because thepressure p_(A) deviates only slightly from the ambient pressure of 1.01bars. The measurement data, i.e., the acquired operating parametermeasurement signals, can be transmitted by cable or wirelessly, in thelatter case by means of a radio module, for example, installed in theblowing lance, to an evaluation and/or process control unit such as acomputer, especially a PC, which is available to the operatingpersonnel. The process variables inlet pressure p₀ and inlet temperatureT₀ directly at the Laval nozzle necessary for the correct theoreticaldesign of a supersonic nozzle according to the isentropic flow filamenttheory and the static (back)pressure p_(A) in the metallurgical vesselcan now be detected continuously by means of the inventive method andthe inventive measurement system as the actual time-dependent values atthe moment in question. These variables p_(0t) and T_(0t) can bemeasured continuously during the blowing process by means of thedetectors and/or sensors mounted in the head of the lance. The staticpressure p_(A) in the metallurgical vessel plays only a subordinate rolein the design process and thus in the automatic regulation of theoperation of the supersonic nozzle(s) in or at their ideal operatingpoint, because it usually fluctuates only moderately around the ambientpressure (1.01 bars±0.2 bar). When the pressure p_(vs) at the valvestation is also measured continuously, the pressure loss Δp_(verl)between the valve station and entrance of the gas into the head of theblowing lance can also be determined continuously during the blowingprocess.

Especially for the realization of the first two aspects of the inventiondescribed above, an advantageous embodiment of the inventive method ischaracterized in that, the inlet pressure p_(0t) of the gas at theentrance to the at least one supersonic nozzle is detected and/ormeasured, especially continuously, by means of at least one pressuresensor mounted in the head of the lance in the area of the at least onesupersonic nozzle during the operation of the blowing lance, especiallyduring a blowing process, preferably an oxygen blowing process; and inparticular in that the inlet temperature T_(0t) of the gas at theentrance to the at least one supersonic nozzle is detected and/ormeasured, especially continuously, by means of at least one temperaturesensor mounted in the head of the lance in the area of the at least onesupersonic nozzle during the operation of the blowing lance, especiallyduring a blowing process, preferably an oxygen blowing process.

It is especially advisable in this case for the feed pressure p_(vs) ofthe gas at a gas feed station installed a certain distance away from theat least one supersonic nozzle to be detected and/or measuredsimultaneously, especially continuously.

In a similar manner, an embodiment of the inventive measurement systemis characterized in that a pressure sensor is mounted in the head of thelance in the area of the at least one supersonic nozzle, which sensor isconnected by appropriate transmission means to the evaluation and/orprocess control unit; detects and/or measures, especially continuously,the inlet pressure p_(0t) of the gas at the entrance to the at least onesupersonic nozzle during the operation of the blowing lance, especiallyduring a blowing process, preferably an oxygen blowing process; andtransmits, preferably on-line, the measurement signal(s) thus acquiredduring the operation of the blowing lance to the evaluation and/orprocess control unit connected to the at least one pressure sensor andthus makes them available for the purpose of controlling the operationof the blowing lance; and/or in that at least one temperature sensor ismounted in the head of the lance in the area of the at least onesupersonic nozzle, which sensor is connected by appropriate transmissionmeans to the evaluation and/or process control unit; detects and/ormeasures, especially continuously, the inlet temperature T_(0t) of thegas at the entrance to the at least one supersonic nozzle during theoperation of the blowing lance, especially during a blowing process,preferably an oxygen blowing process; and transmits, preferably on-line,the measurement signal(s) thus acquired during the operation of theblowing lance to the evaluation and/or process control unit connected tothe at least one temperature sensor and thus makes them available forthe purpose of controlling the operation of the blowing lance.

According to a third aspect of the invention, it is provided that, bymeans of at least one vibration sensor installed directly in the head ofthe lance, the vibration amplitude A and/or the vibration frequency ω ofthe blowing lance, especially an oxygen blowing lance, is detected andmeasured during the operation of the blowing lance. As a result of themeasurement by means of detectors and/or sensors mounted in the head ofthe lance, it is possible to achieve a reliable, maintenance-free andefficient vibration measurement at the blowing lance in themetallurgical vessel, especially a converter, so that the increase inthe level of the slag and the possible ejection of slag from the vesselcan be recognized as well as the presence of skull on the blowing lance.It is therefore possible to measure the vibrations of the blowing lance,especially an oxygen blowing lance or BOF lance, by means of a sensorsystem mounted inside the blowing lance. The measurement is made in thehead of the lance at a point as close as possible to the orifice, thatis, at the “low point” of the blowing lance, and as a result themeasurement signals are highly significant, in fact more significantthan those according to the prior art. The measurement is preferablycarried out by means of a wireless sensor system (detectors and/orsensors), wherein, however, a hardwired system or system withtransmission lines is also possible. The latter possibility, however, isassociated with certain problems, namely, that, if the lower part of thelance, that is, the head of the lance located above the sensor systemformed by the detectors and/or sensors, is damaged, the feed lines andpossibly the sensor system itself may have to be replaced, which isexpensive. In the case of vibration sensors as well, power can besupplied to the wireless sensor system by batteries, accumulators, or anenergy-harvesting module.

For the realization of this third aspect of the present invention, thethird aspect is characterized in that the vibration amplitude A and/orthe vibration frequency ω of the blowing lance is detected and/ormeasured in the head of the lance, especially continuously, by means ofat least one vibration sensor mounted in the head of the lance in thearea of the at least one supersonic nozzle during the operation of theblowing lance, especially during a blowing process, preferably an oxygenblowing process.

In a similar manner, it is provided in accordance with an embodiment ofthe measurement system, that at least one vibration sensor is mounted inthe head of the lance in the area of the at least one supersonic nozzle,which sensor is connected by appropriate transmission lines to theevaluation and/or process control unit; detects and/or measures in thehead of the lance, preferably continuously, the vibration amplitude Aand/or the vibration frequency ω of the blowing lance during theoperation of the blowing lance, especially during a blowing process,preferably an oxygen blowing process; and transmits, preferably on-line,the measurement signal(s) thus acquired during the operation of theblowing lance to the evaluation and/or process control unit connected tothe at least one vibration sensor and thus makes them available for thepurpose of controlling the operation of the blowing lance.

By means of the vibration sensors mounted in the head of the lance todetermine the vibration amplitude A and/or the vibration frequency ω ofa gas blowing lance, especially an oxygen blowing lance, it is possibleto measure the amplitude and/or frequency of the vibrations continuouslyand, in association with that, to monitor the height of the slag in theconverter or metallurgical vessel. When the level of the slag is low,the frequency spectrum is dominated by the natural harmonic vibrationsof the blowing lance. When the level of the slag is high, the lance isenclosed by the slag. A stochastic component of the vibrations, causedby the slag, now develops and increases. The formation of skull on thetip of the lance also changes the mass of the lance. The amount ofadhering slag or steel can be estimated by measuring the naturalfrequencies, and an early decision can be made about replacing thelance. The measured vibration amplitudes A and/or vibration frequenciesw are also transmitted, especially in a wireless manner and inparticular by radio, to the evaluation and/or process control unit,especially a computer, preferably a PC, which is available to theoperator for use. At least one radio module is assigned to theassociated vibration sensor or sensors and is connected to it or tothem.

According to a fourth aspect, photodiodes, photodetectors, or lightsensors, especially CCD (Charge-Coupled Device) sensors or CMOS(Complementary Metal Oxide Semiconductors; metal-oxide semiconductors)are arranged inside the head of the lance to detect, in the head of thelance, the optical emissions which occur during a blowing process uponignition of the oxygen jets. This makes it possible to detect in realtime when an oxygen blowing lance ignites, wherein the photodiode or theat least one optical sensor or detector is arranged inside the blowinglance in such a way that the optical emissions of the arcing zone causedby the ignition of the oxygen jets can be detected by the sensor insidethe blowing lance. The measurement signals thus obtained can then besubjected to further processing in the assigned evaluation and/orprocess control unit. In this case as well, the measurement signals anddata are transmitted over a cable or wirelessly by radio. Again, powercan be supplied to the wireless optical sensor system by means ofbatteries, accumulators, or an energy-harvesting module.

The light sensors (CCD sensors, CMOS sensors) or a camera comprisingsuch sensors, diodes, or detectors for determining the time whenignition occurs during the oxygen blowing process are installed directlyin the head of the lance. It is provided in this case that one or morelight sensors are arranged in the interior of the blowing lance,preferably in the head of the lance, in order that the exact time ofignition can be determined. The optical emission associated with theignition of the oxygen jets is detected by the sensor or sensors insidethe head of the blowing lance, and the measurement signals and theassociated information thus acquired are transmitted to the evaluationand/or process control unit, especially to a computer or PC, either inhardwired fashion over a cable or wirelessly by radio.

To implement the above-described fourth aspect of the invention, oneembodiment of the method is characterized in that the opticalemission(s) which occur when the oxygen jets are ignited is/are detectedin the head of the lance by means of at least one light sensor,especially a CCD or CMOS sensor, or by at least one camera equipped withsuch a sensor arranged in the head of the lance in the area of the atleast one supersonic nozzle during the operation of the blowing lance,especially during a blowing process, preferably an oxygen blowingprocess. In an embodiment of the measurement system, it is similarlyprovided that at least one light sensor, especially a CCS or CMOSsensor, or at least one camera equipped with such a sensor is arrangedin the head of the lance in the area of at least one supersonic nozzle,which sensor or sensor-equipped camera is connected by appropriatetransmission means to the evaluation and/or process control unit;detects and/or measures in the head of the lance the optical emission(s)which occur when the oxygen jets ignite during the operation of theblowing lance, especially during a blowing process, preferably an oxygenblowing process; and transmits, preferably, on-line, the measurementsignal(s) thus obtained during the operation of the blowing lance to theevaluation and/or process control unit connected to the at least onelight sensor, especially a CCS or CMOS sensor, or to the at least onecamera and thus makes them available for the purpose of controlling theoperation of the blowing lance.

With the inventive embodiment according to the fourth aspect, anaccurate determination of the time of ignition can be made; and if asensor/detector is assigned to each supersonic nozzle of a multi-holeblowing lance, the ignition time can also be differentiated with respectto the individual oxygen jets.

A fifth aspect of the invention has the goal of detecting and/ormeasuring the place where ignition occurs during the oxygen blowingprocess. In this regard, light sensors, especially CCD or CMOS sensorsor detectors, photodiodes, or photodetectors or a camera equipped withsuch components should be arranged directly in the head of the lance,and the sensor surfaces receiving the incident light should be aimedoptically through an orifice of the blowing lance and especially theorifice of an assigned supersonic nozzle. The light sensors installed inthis way in the head of the lance serve to determine the place whereignition occurs during the oxygen blowing process. When several properlyaimed optical sensors are used or when a camera is used, it is possibleto determine not only the time of ignition but therefore also, in thecase of the multi-hole blowing lances conventionally used, the placeswhere ignition occurs. Because, in the normal case, the head of ablowing lance contains several supersonic nozzles, a light sensor can beassigned to each nozzle. In this way, it becomes possible to recognizethe ignitions of the oxygen jets in a differentiated manner, because,when an oxygen jet strikes the liquid pig iron, an arcing zone isformed, whereas, when the arcing zone strikes scrap, no arcing zone isformed, so that the areas detected in the case in question will differwith respect to their optical emission(s). The advantage of theinstallation in the interior of the blowing lance is that the sightingopening of the camera or of the sensors is continuously flushed clean bythe flow of oxygen. The measurement signals obtained can then betransmitted over a cable or by radio to the evaluation and/or processcontrol unit, especially a computer or PC, and used there for thepurpose of process control. This fifth aspect of the invention thereforeconsists in detecting the place where the oxygen jet ignites byinstalling an optical sensor or detector inside the blowing lance insuch a way that it can detect, from inside the blowing lance, theoptical emissions of the arcing zone caused by the ignition of theoxygen jets, and thus so that the measurement signals or data thusobtained can then be subjected to further processing in the assignedevaluation and/or process control unit. The data are transmitted eitherin hardwired fashion over a cable or in wireless fashion by radio. Inthis case as well, the power can be supplied to the wireless opticalsensor system by means of batteries, accumulators, or anenergy-harvesting module, wherein the detector(s) or sensor(s) is/aresupplied with electric power by means of a energy-harvesting moduleinstalled in the blowing lance.

To realize this fifth aspect of the invention, the inventive method ischaracterized in that the optical emissions occurring outside the lanceare detected in the head of the lance by means of at least one lightsensor, especially a CCD or CMOS sensor, or at least one camera equippedsuch a sensor arranged in the head of the lance in the area of the atleast one supersonic nozzle and aimed optically through an orifice ofthe blowing lance during the operation of the blowing lance, especiallyduring a blowing process, preferably an oxygen blowing process.

The measurement system for realizing this fifth aspect of the inventionis characterized similarly in that at least one light sensor, especiallya CCD or CMOS sensor, or at least one sensor-equipped camera is arrangedin the head of the lance, in the area of the at least one supersonicnozzle, which sensor or sensor-equipped camera is optically aimeddirectly through an orifice of the blowing lance; is connected inhardwired fashion to the evaluation and/or process control unit; detectsand/or measures, in the head of the lance, the optical emissionsoccurring outside the blowing lance during the operation of the blowinglance, especially during a blowing process, preferably an oxygen blowingprocess; and transmits, preferably on-line, the measurement signal(s)thus obtained during the operation of the blowing lance to theevaluation and/or process control unit connected to the at least onelight sensor or the at least one camera and makes them available for thepurpose of controlling the operation of the blowing lance.

In the case of a multi-hole lance comprising several supersonic nozzles,it is especially advisable for at least one detector or sensor to beassigned to each supersonic nozzle or assigned in the case of acorresponding blowing lance of the measurement system.

According to a further elaboration of the method and of the measurementsystem, one or more detectors or sensors from the group consisting ofpressure sensors, temperature sensors, vibration sensors, and/or lightsensors are assigned to the blowing lance, or the blowing lancecomprises one or more detectors or sensors from the group consisting ofpressure sensors, temperature sensors, vibration sensors, and/or lightsensors.

The transmission of the measurement data to the evaluation unit such asa PC and the power supply to the measuring sensors or detectors can beprovided over a cable, for example. When the blowing lance is replaced,however, the head of the lance or the lower part of the lance is usuallycut off because of wear, the presence of skull, or damage. In the caseof a hardwired power supply, there is the danger that the cable willalso be cut. A wireless method of measurement signal and measurementdata transmission is therefore especially advantageous. This can bedone, for example, by means of radio transmission. In this case, thesensor or detector in question can be equipped with a battery or anenergy-harvesting module to guarantee the power supply. In a furtherelaboration, therefore, the inventive method is characterized in thatthe measurement signal(s) originating from the detector and/or sensoris/are transmitted to the evaluation and/or process control unit inhardwired fashion by means of a cable arranged in or on the blowinglance or in wireless fashion by means of a radio module connected to thedetector and/or sensor and arranged in the blowing lance.

It is also advantageous in this case for the detector(s) or sensor(s) tobe supplied with electric power by an energy-harvesting module arrangedin the blowing lance.

In an advantageous elaboration of the invention, the measurement systemis characterized, finally, in that the detector(s) or sensor(s) is/areconnected in hardwired fashion to the evaluation and/or process controlunit by means of a cable arranged in the blowing lance or in wirelessfashion by means of a radio module arranged in the blowing lance,wherein in particular the detector(s) or sensor(s) connected in wirelessfashion to the evaluation and/or process control unit is/are preferablyconnected to an energy-harvesting module arranged in the blowing lance.

The above-mentioned detectors and/or sensors can thus be equipped with awireless data and/or power transmission system inside the blowing lance.As a result, the effort required to install new sensors and/or detectorsis less than it would be in the case of hardwired or cabled sensors ordetectors. This reduced effort for reinstallation is especiallyadvantageous when the blowing lance must be cut off above the sensorsbecause of, for example, the presence of skull on the blowing lance, sothat a new lance part can be welded on. The sensors, designed aswireless components in this sense, can be equipped with anenergy-harvesting source or energy-harvesting module to avoid the needto replace the power source. A generator, for example, can serve as anenergy source in the lance, which extracts its energy from the flow ofgas or from the vibration of the lance. In cases where vibrations arebeing measured and an energy-harvesting module is used, the energy canbe can be derived from the vibrations of the blowing lance.

When several properly oriented optical sensors or detectors or a cameraequipped with such sensors is used, it is possible to determine not onlythe time when ignition occurs but also, in the case of the conventionalmulti-hole blowing lances, the locations where the ignitions occur.Because the head of a blowing lance usually contains several supersonicnozzles, a corresponding light sensor or detector can be assigned toeach supersonic nozzle. In this way, there is the possibility ofdetecting the ignitions of the oxygen jets in a differentiated manner.

With the help of the evaluation and/or process control unit, themeasurement signals detected or measured or determined by the sensorsand/or detectors or the data derived from those signals can be evaluatedand used for the purpose of controlling the process and the operation ofthe model on which the process is based.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of the disclosure. For a better understanding of the invention, itsoperating advantages, specific objects attained by its use, referenceshould be had to the drawings and descriptive matter in which there areillustrated and described preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWING

In the drawing:

FIG. 1 shows a schematic cross section of a blowing lance with anassociated metallurgical vessel and gas supply;

FIG. 2 shows a schematic diagram of the area of the head of a lance witha hardwired sensor arranged therein;

FIG. 3 shows a schematic diagram of the area of the head of a lance witha wireless sensor installed therein; and

FIG. 4 shows a schematic diagram of a sensor system for detecting thelocations where the ignitions occur.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a blowing lance 2, especially an oxygen blowing lance,which has been introduced from above into a metallurgical vessel 1designed as a converter; when in operation in the working position shownin FIG. 1, the lance blows gas onto a metal bath 3 in the metallurgicalvessel 1. At the end of the blowing lance 2 located at the bottom in thediagram of FIG. 1, a replaceable head 4 is mounted, which forms the tipof the blowing lance. Inside the head 4 of the lance are severalsupersonic nozzles, which are indicated by the dashes proceeding fromthe head 4 of the lance.

Through a feed line 5 consisting of pipes or hoses, the blowing lance 2is connected to a gas feed station 6, which comprises a valve station 7,by means of which the gas 8 to be blown out from the head 4 of the lancecan be supplied in regulated fashion to the feed line 5. In theexemplary embodiment, the gas 8 is a gas used in oxygen blowingprocesses, that is, oxygen or an oxygen-containing gas mixture such asan argon-oxygen gas. It is also possible, however, to supply nitrogen ora nitrogen-containing gas mixture to the feed line 5. When gas 8 isflowing into the feed line 5, a pressure p_(vs), called the upstreampressure, can be adjusted and automatically regulated at the valvestation 7. The pressure p_(vs) is measured continuously during theoperation of the blowing lance 2 for process control purposes.

In the metallurgical vessel 1 or converter, a static (back)pressurep_(A) is present during the operation of the blowing lance 2. Theindividual supersonic or Laval nozzles in the head 4 of the lance aredesigned for an ideal operating point (design point), at which thedesign pressure p₀ and the design temperature T₀ are present at theentrance to each of the supersonic nozzles. During the operation of theblowing lance 2, the inlet pressures p_(0t) and the individual inlettemperatures T_(0t) currently prevailing at the entrance to each of thesupersonic or Laval nozzles are continuously detected and/or measured.Because the pressure loss Δp_(verl) from the valve station to theentrance area of each supersonic nozzle is determined by therelationship Δp_(verl)=p_(vs)−p_(0t), it is possible to perform anon-line calculation of the pressure loss Δp_(verl) and thus to monitorthe deviation between the inlet pressure p_(0t) and of the inlettemperature T_(0t) of the oxygen supplied to the individual supersonicnozzles from the design variables p₀ and T₀ during the blowing process.In this way, the upstream pressure p_(vs) at the valve station 7 can beadjusted in such a way that the correct design pressure p₀ is present asthe inlet pressure p_(0t) at the entrance to each supersonic or Lavalnozzle.

The inlet pressure p_(0t) and the inlet temperature T_(0t) are acquiredby means of a detector or sensor 9 a, 9 b, which is arranged in head 4of the lance in such a way that it detects and/or measures, at theentrance to all or at least one of the supersonic nozzles assigned toit, the inlet pressure p_(0t) and/or the inlet temperature T_(0t) of thegas 8 to be blown. If a detector or sensor 9 a, 9 b is assigned to theentrance of each supersonic nozzle, then the number of detectors and/orsensors 9 a, 9 b arranged in the head 4 of the lance will be the same asthe number of Laval or supersonic nozzles.

FIGS. 2 and 3 show schematically the arrangement of the least one sensoror detector 9 a, 9 b. FIG. 2 shows a detector or sensor 9 a arranged bymeans of a bracket 10 in the head 4 of the lance; the sensor or detectoris connected to an evaluation and/or control unit (not shown) by atransmission line, especially a cable 11.

In the case of the exemplary embodiment according to FIG. 3, a detectoror sensor 9 b is used, which is connected to an assigned radio module12, by means of which the measurement signals detected and/or measuredby the detector or sensor 9 b are transmitted in wireless fashion,especially by radio, to the evaluation and/or control unit (not shown).The radio module 12 comprises here a power source in the form of abattery or energy-harvesting module.

The measurement signals acquired by means of the at least one detectoror sensor 9 a, 9 b are transmitted continuously, on-line, during theoperation of the blowing lance 4 in the blowing process to the connectedevaluation and/or process control unit (not shown), where they are madeavailable for the purpose of controlling the operation of the blowinglance 2 and then used in fact to control the blowing process.

The at least one detector or sensor 9 a, 9 b is a pressure sensor fordetermining the inlet pressure p_(0t). It is also quite possible,however, for several detectors or sensors 9 a, 9 b or multi-functiondetectors or sensors to be arranged in the head 4 of the lance, thesecomponents being selected from the group consisting of pressure sensors,temperature sensors, vibration sensors, and/or light sensors.

Vibration sensors installed in the head 4 of the lance detect and/ormeasure the vibration amplitude A and/or the vibration frequency ω ofthe blowing lance 2.

Detectors or sensors 9 a, 9 b designed as light sensors detect theoptical emissions caused by the ignition of oxygen jets as the oxygen isbeing blown into the vessel. The light sensors can be CCD sensors, CMOSsensors, photodiodes, photodetectors, or cameras equipped with thesesensors or detectors. In the head 4 of the lance, they detect theradiation or optical emission occurring when an oxygen jet ignites; orthey detect, in the head 4 of the lance, the change in the radiationintensity or in the optical emissions occurring when an oxygen jetignites. The individual detector or sensor 9 a, 9 b designed in the formof a light sensor can also be equipped and aimed in such a way that, asindicated schematically in FIG. 4, it can detect or recognize thelocation where the ignition occurs, i.e. the ignition spot 13. In caseswhere at least one, preferably several, aimed optical sensors 9 a, 9 bare used or when a camera is used as an optical sensor system, it ispossible to determine not only the time when ignition occurs but also,in the case of conventionally used multi-orifice blowing lance, theignition spot 13. Here, use is made of the effect that, when an oxygenjet 8 b emerging from the head 4 of the lance strikes the metal bath 3in the metallurgical vessel 1, an arcing zone is formed upon ignition ofthe oxygen jet 8 b at the ignition spot 13, whereas, when an oxygen jet8 a strikes scrap 14 present in the metal bath 3, an arcing zone is notformed. The point of contact of the oxygen jet 8 b therefore shows adifferent radiation intensity and thus optical emission than the contactpoint of the oxygen jet 8 a. Advantage can be taken of this effect todetect the arcing zone and thus the ignition spot 13.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the inventive principles, it will beunderstood that the invention may be embodied otherwise withoutdeparting from such principles.

We claim:
 1. A method for operating a blowing lance for blowing a gas ina metallurgical vessel, wherein a replaceable head of the blowing lancecomprises at least one supersonic nozzle, the method comprising thesteps of: detecting and/or measuring inlet pressure and/or inlettemperature of the gas at the at least one supersonic nozzle and/orvibration amplitude and/or vibration frequency of the blowing lanceand/or a time at which ignition occurs during an oxygen blowing processand/or a location at which ignition occurs during the oxygen blowingprocess, in the head of the lance with a detector or sensor arranged inthe head of the lance in an area of the supersonic nozzle duringoperation of the blowing lance; and transmitting measurement signal(s)thus acquired during the operation of the blowing lance, to anevaluation and/or process control unit connected to the detector orsensor and making the signals available for controlling the operation ofthe blowing lance.
 2. The method according to claim 1, wherein the inletpressure of the gas at an entrance to the at least one supersonic nozzleis detected and/or measured in the head of the lance by at least onepressure sensor arranged in the head of the lance in the area of the atleast one supersonic nozzle during operation of the blowing lance. 3.The method according to claim 1, wherein the inlet temperature of thegas at an entrance to the at least one supersonic nozzle is detectedand/or measured in the head of the lance by at least one temperaturesensor arranged in the head of the lance in the area of the at least onesupersonic nozzle during the operation of the blowing lance, especiallyduring a blowing process, preferably an oxygen blowing process.
 4. Themethod according to claim 1, further comprising simultaneously detectingand/or measuring feed pressure of the gas at a gas feed station locateda distance away from the at least one supersonic nozzle.
 5. The methodaccording to claim 1, wherein the vibration amplitude and/or thevibration frequency of the blowing lance is detected and/or measured inthe head of the lance by at least one vibration sensor arranged in thehead of the lance in the area of the at least one supersonic nozzleduring the operation of the blowing lance.
 6. The method according toclaim 1, further comprising detecting optical emission(s) occurring uponignition of oxygen jets in the head of the lance by at least one lightsensor arranged in the head of the lance in the area of the at least onesupersonic nozzle during the operation of the blowing lance.
 7. Themethod according to claim 1, further comprising detecting opticalemissions occurring outside the blowing lance in the head of the lanceby at least one light sensor or at least one camera equipped with alight sensor, which is arranged in the head of the lance in the area ofthe at least one supersonic nozzle and is optically aimed directlythrough an orifice open of the blowing lance.
 8. The method according toclaim 1, wherein the lance is a multi-hole lance comprising severalsupersonic nozzles, at least one detector or sensor being assigned toeach supersonic nozzle.
 9. The method according to claim 1, wherein atleast one detector or sensor selected from the group consisting ofpressure sensors, temperature sensors, vibration sensors, and/or lightsensors, is assigned to the blowing lance.
 10. The method according toclaim 1, including transmitting the acquired measurement signal(s) fromthe detector or sensor to the evaluation and/or process control unit inhardwired fashion by a cable arranged in or on the blowing lance or inwireless fashion by a radio module connected to the detector and/orsensor and arranged in the blowing lance.
 11. The method according toclaim 1, including supplying the detector(s) or sensor(s) with electricpower by an energy-harvesting module arranged in the blowing lance. 12.A measurement system for determining measurement signals used forprocess control during operation of a blowing lance for blowing gas in ametallurgical vessel, wherein the measurement system comprises: ablowing lance with a replaceable head having at least one supersonicnozzle; an evaluation and/or process control unit for receiving andprocessing measurement signals; and a detector or sensor arranged in thehead of the lance in an area of the at least one supersonic nozzle,which detector or sensor is connected to the evaluation and/or processcontrol unit, detects and/or measures in the head of the lance duringthe operation of the blowing lance inlet pressure and/or inlettemperature of gas at the at least one supersonic nozzle and/orvibration amplitude and/or vibration frequency of the blowing lanceand/or a time when ignition occurs during an oxygen blowing processand/or a location where ignition occurs during the oxygen blowingprocess, and transmits the measurement signal(s) acquired duringoperation of the blowing lance to the evaluation and/or process controlunit connected to the at least one detector or sensor so that thesignals are available for controlling operation of the blowing lance.13. The measurement system according to claim 12, wherein the detectoror sensor is at least one pressure sensor arranged in the head of thelance in the area of the at least one supersonic nozzle, which sensordetects and/or measures, in the head of the lance, the inlet pressure ofthe gas at an entrance to the at least one supersonic nozzle duringoperation of the blowing lance, and transmits the measurement signal(s)to the evaluation and/or process control unit for controlling theoperation of the blowing lance.
 14. The measurement system according toclaim 12, wherein the detector or sensor is at least one temperaturesensor arranged in the head of the lance in the area of the at least onesupersonic nozzle, which sensor detects and/or measures, in the head ofthe lance the inlet temperature of the gas at an entrance to the atleast one supersonic nozzle during the operation of the blowing lance,and transmits the measurement signal(s) to the evaluation and/or processcontrol unit for controlling the operation of the blowing lance.
 15. Themeasurement system according to claim 12, wherein the detector andsensor is a vibration sensor arranged in the head of the lance in thearea of the at least one supersonic nozzle, which sensor detects and/ormeasures, in the head of the lance, the vibration amplitude and/or thevibration frequency of the blowing lance during operation of the blowinglance, and transmits the measurement signal to the evaluation andprocess control unit for controlling the operation of the blowing lance.16. The measurement system according to claim 12, wherein the detectoror sensor is at least one light sensor or at least one camera equippedwith a light sensor arranged in the head of the lance in the area of theat least one supersonic nozzle, which sensor or sensor-equipped cameradetects and/or measures, in the head of the lance, optical emission(s)occurring when oxygen jets ignite during the operation of the blowinglance, and transmits the measurement signal(s) to the evaluation and/orprocess control unit for controlling the operation of the blowing lance.17. The measurement system according to claim 12, wherein the detectoror sensor is at least one light sensor or at least one camera equippedwith a light sensor arranged in the head of the lance in the area of theat least one supersonic nozzle, which sensor or sensor-equipped camerais optically aimed directly through an orifice of the blowing lance,detects and/or measures, in the head lance, optical emissions occurringoutside the lance during the operation of the blowing lance, andtransmits the measurement signal(s) to the evaluation and/or processcontrol unit for controlling the operation of the blowing lance.
 18. Themeasurement system according to claim 12, wherein the blowing lance is amulti-hole lance with multiple supersonic nozzles, wherein at least onedetector or sensor is assigned to each of the supersonic nozzles. 19.The measurement system according to claim 12, wherein the blowing lancecomprises at least one detector or sensor selected from the groupconsisting of pressure sensors, temperature sensors, vibration sensors,and/or light sensors.
 20. The measurement system according to claim 12,wherein the detector or sensor is connected to the evaluation and/orprocess control unit in a hardwired manner by a cable arranged in or onthe blowing lance or in a wireless manner by a radio module arranged inthe blowing lance, wherein when the detector or sensor is wirelesslyconnected to the evaluation and/or process control unit the detector orsensor is connected to an energy-harvesting module installed in theblowing lance.